Centrifugal pumps



1964 K. E. NICHOLS ETAL 3,

CENTRIFUGAL PUMPS Filed Feb. 20, 1961 2 Sheets-Sheet l {NVENTORSi Dec. 22, 1964 K. E. NICHOLS ETAL 3,162,135

CENTRIFUGAL PUMPS 2 Sheets-Sheet 2 Filed Feb. 20. 1961 United States Patent 3,162,135 CENTRIFUGAL PUMPS Kenneth E. Nichols, Westminster, Ciifiord N. Hall, Denver, and Anthony Malgieri, Broomiield, (1010., assignors to Sundstrand Corporation, a corporation of Illinois Filed Feb. 20, 1961, Ser. No. 90,393

6 Claims. (Cl. 103-403) This invention relates to centrifugal pumps and more particularly to a highly eflicient and reliable pump to be utilized in critical installations such as aircraft.

In relationship to aircraft engines and systems, centrifugal pumps are used in many ways. These uses include oil pumps for lubricating systems, pumps for hydraulic control systems and water pumps for water injection-systems. For such aircraft utilization, it is desirable to reduce to a minimum the possibility of failure in flight. At the same time, it is desirable to have the pumps as efli- .cient as possible so that they can accomplish the designed requirements while requiring a minimum of power to operate them.

It is an object of the present invention to provide a new and improved centrifugal pump.

Another object is to provide a centrifugal pump which will have both a high efliciency and a low probability of failure.

A further object is to provide a centrifugal pump having stiffeners on one edge of the impeller blade to reduce vibration and the possibility of fatigue failure.

A still further object is to provide a more eflicient impeller housing having an annulus with a semi-circular cross section equal to the throat diameter of the difiuser.

Still another object of the present invention is to provide a more eflicient centrifugal pump impeller by having blades Which are rounded off on the leading side to a thin tip.

An additional object of the present invention is to provide a more efficient centrifugal pump having a double cone diffuser wherein the first cone has the optimum diffuser angle and the second cone has a steeper cone angle slightly greater than the optimum.

Yet another object of the present invention is to provide a centrifugal pump having a short spiral section machined into the casing ahead of the difiuser throat for improved efliciency.

A further object of the present invention is to provide an improved dynamic seal between the drive shaft and the housing of a centrifugal pump.

A still further object is to provide a drainage system to prevent fluid from leaking from the pump along the drive shaft when the pump is either stopped or operating at a low rotational velocity.

Another object of the present invention is to provide a removable diffuser for a centrifugal pump.

Still another object is to provide a centrifugal pump diffuser having a throat portion composed of a different material than that of the diffuser body.

Further objects and advantages will become apparent from the following detailed description taken in connection with the accompanying drawings.

In the drawings:

FIGURE 1 is a sectional view taken along a vertical plane through the center line of an embodiment of the present invention;

FIGURE 2 is a sectional view taken along the line 2.2

of FIGURE 1;

FIGURE 3 is a sectionalview taken along the line 3-3 of FIGURE 1.

While this invention is susceptibleof embodimentsin many different forms, there is shownin the drawings and 'ice of the invention will be pointed out in the appendedclaims.

Referring first to FIGURE 1, a centrifugal pump housing comprising a cover member 10, a base member 11, and a sealing member 12 is secured to a supporting member 13. A bolt 14 is one of a set of bolts securing the housing cover member 10 to the support member 13. An impeller drive shaft 15 is rotatably mounted in the support member 13 by a bearing sleeve 16. The housing base member 11 has an O ring 17 retained in a groove 18 to prevent fluid leakage between the housing cover member 10 and the base member 11. The sealing member 12 abuts the base member 11 and has an O ring 19 secured in a groove 20 to prevent fluid leakage between it and the housing cover member 10.

An impeller hub 21 is secured to one end of the shaft 15 by a bolt 22. A set of eight impeller blades is secured to the hub 21. An impeller blade 23 and an impeller blade 24 of the set of impeller blades are shown in FIGURE 1. The set of impeller blades 23 through 2% are shown in FIGURE 2. Each blade has its leading side rounded off on a large radius to produce a thin blade tip.

A rigid stiffener is secured to the trailing edge of each blade. In FIGURE 1, a stiffener 30 is shown secured to the impeller blade 23 and a stiffener 31 is shown secured to the impeller blade 24. The remaining six stiffeners on the other six blades are not shown in the drawings. As the blades are rotated with the hub 21, the stiffeners rotate in the recess 32. A semi-circular annulus 33 is formed in the housing cover member 10 surrounding the tips of the impeller blades.

An intake duct 34 provides a passage through which fluid is drawn to the impeller blades. A slinger'member 35 is mounted on shaft 15 to rotate therewith. An 0 ring 36 is retained in a slot 37 between the shaft 15 and the slinger member 35 to prevent the leakage of fluid along the shaft 15. A disc 38 is secured on the shaft 15 adjoining the slinger member 35. A retaining ring 39 is mounted on the shaft 15 between the disc 38 and a shoulder 40 of the drive shaft 15.

Referring now to FIGURE 2, a diffuser 41 is mounted in a bore 42 in the housing cover member 10. A locking bolt 43 is threaded into. an aperture 44 in the housing 10 to secure the diffuser 41. A diffuser throat member 45 is mounted in a recess 46 of the diifuser 41.

The annulus 33 is positioned at a constant radius from the center of the hub 21 except for an annulus section 47 ahead of a diffuser throat 48. As shown in FIGURE 2 this section 47 of the annulus 33 departs from a constant radius in a short logarithmic spiral to connect with the diffuser throat 48 formed in diffuser throat member 45.

The diffuser throat 48 is joined to a first cone portion 49 which has anoptimum cone angle. The first cone portion 49 is joined to a second cone portion 50 which has a'steeper cone angle.

Referring again to FIGURE 1 .a set of leakage ports are provided in the housing base member 11. A cavity 52 exists between the sealing member 12 and the supporting member 13. The cavity 52 is ventedby a set of drain holes. One of these drain holes 53 is shown in FIGURE 1.

FIGURE 3 shows a set of vanes 54 forming a part of the slinger member 35. g,

The fluid to be pumped such as oil, hydraulic fluid or water is drawn through the duct 34 to the impeller blades. The impeller blades are driven from a suitable power l at the outer diameter of the shaft.

source (not shown) through the drive shaft 15 and the hub 21. The centrifugal force imparted to the fluid by the rotation of the impeller blades forces it out into the semi-circular annulus 33 and into the diffuser 41. The diffuser converts the kinetic energy imparted to the fluid by the rotation of the impeller blades into fluidpressure.

The 'stiffeners such as 30 and 31 reduce blade vibrations and thereby reduce the possibility of fatigue failure. Since they run in the recess 32 they do not affect the operation of the impeller blades. The use of individual .stiffeners instead of a complete flange or shroud is an important advantage in that the pressure at the shaft seal is much less than the maximum pressure that is present .wetted perimeter of the annulus over the usual rectangular annulus employed in normal Centrifugal pumps. With a diameter equal to the throat diameter of the diffuser 41 and the diffuser throat 48 relatively free of discontinuities, the best diffuser inlet conditions are provided. Thus the semi-circular annulus 33 increases the pressure recovery in the diffuser 41. Both these eifects increase the pump elficiency.

The rounding off of the leading sides of the impeller blades to as thin a tip as possible with a large radius minimizes interferences to flow as the blade tips rotate past the diffuser inlet.

The first cone portion 49 of the diffuser 41 is designed to have an optimum diffuser angle. Since it would be impractical in most aircraft installations to make the diffuser sufficiently long for the optimum cone to reach the diameter of a discharge pipe, the second cone portion 50 has a slightly steeper cone angle than the optimum. Thus the double cone diffuses the throat velocity down to discharge pipe velocity with no abrupt discontinuities in the flow path in a shorter length than would be possible if the optimum angle'cone were carried out far enough to reach the diameter of a discharge pipe. The reduced length of the diffuser reduces the skin friction which partially off-sets the diffuser friction in the second cone 5%.

The short logarithmic spiral section 47 machined into the casing ahead of the dilfuser throat 48, provides a path for the fluid leaving the blades which allows it to flow to the diffuser throat without forcing it away from the path which it naturally tends to follow.

Referring again to FIGURES 1 and :3, slinger member 35 provides a dynamic shaft seal. Inlet pressure is exerted against the right hand face of the slinger member 35 The side of the housing base member 11 facing the slinger member 35 is smooth and therefore imparts relatively little pressureto the fluid. Therefore the fluid. at the outer diameterof slinger member 35 is at a pressure only slightly greater than inlet pressure. .The vanes 54 on the left hand side of the slinger .35 can impart a considerable pressure to fluid trapped in them. Therefore, fluid will travel down the left side of the slinger only far enough to produce a pressure at the slinger member outer diameter equal to inlet pressure plus the pressure increase on the right hand, fam of the slinger member 35. The leakage ports 51 provide paths for fluid to flow back tothe impeller blades. 7 V p, V I

If fluid is, fed to the pump while it is standing still or rotating at low speed it will pass by'the dynamic seal and continue alongthe shaft 15. The clearance between the sealingmember 12 and the slinger member 35, is small. Fluid passing through the clearance must therefore do it at a slow rate compared to the rate at which the cavity 52. between sealing memberlZ and support member 13 and drain holes such as 53. can, vent such leakage overboard. Thus the need for any mechanical seal-between the pump housing and the drive shaft 15 is eliminated. The disc 38 deflectstowards the'drain' holes any fluid spraying out through the clearance between the sealing member 12 and slinger member 35 into cavity 52.

Since the diffuser is a separate piece, it is possible to guickly replace it if replacement should become necessary. In addition this permits a flexibility in changing pump impellers while at the same time maintaining a proper tangential relationship between the impeller blades and the dilfuser throat 48. Also a more corrosion resistant material may be utilized for the diffuser than would be desirable for the construction of the entire housing.

Since the throat insert 45 is a separate piece, it may be made of a material such as ceramic or tungsten carbide without having to make the entire diffuser out of such a material. It has been found that the diffuser throat is subject to much more erosion than any other portion of a centrifugal pump.

We claim:

1. In a centrifugal pump, the combination of an impeller comprising a hub and a set of impeller blades mounted on said hub, an impeller housing surrounding said impeller, an annulus having a semi-circular cross section in said impeller housing surrounding said impeller blades, a cone diffuser passage in said housing, and a logarithmic spiral section in said annulus and extending over less than a 90 arc of said annulus to connect said annulus to said diffuser passage.

2. In a centrifugal pump, the combination of an impeller comprising a hub and a set of impeller blades mounted on said hub, an impeller housing surrounding said impeller, an annulus in said impeller housing surrounding said impeller blades, a cone diffuser passage in said housing, and a logarithmic spiral section in said annulus and extending over less than a 90 arc of said annulus to connect said annulus to said diffuser passage.

3. In a centrifugal pump, the combination of an impeller, said impeller comprising a hub and a set of impeller blades, an impeller housing surrounding said impeller, an annulus in said impeller housing surrounding said impeller blades, a removable member having a double cone diffuser passage in said housing, said diffuser passage being composed of a first cone portion having an optimum diffuser cone angle and a second cone portion having a steeper diffuser cone angle joining said first cone portion, and a logarithmic spiral section in said annulus to connect said annulus to said first cone portion of said diffuser passage.

4. In a centrifugal pump, the combination of a drive shaft; a main impeller rigidly secured on one end of said drive shaft; said impeller comprising a hub, a set of impeller blades mounted on said hub having the leading side rounded to a thin tip, and a rigid stiffening member secured to the one edge of said blade; an impeller housing surrounding said impeller having an aperture therein for rotatable mounting of said drive shaft; a fluid inlet passage through said impeller housing to said impeller blades; an annulus having a semi-circular cross section in said impeller housing surrounding said impeller blades; a removable member having a double cone diifuser passage therein, said removable member mounted in an aperture in said housing, said diffuser passage being composed of a first cone portion having an optimum diffuser cone angle and a second cone portion having a steeper diffuser angle; a logarithmic spiral section in said annulus to connect said annulus to said first cone portion of said diffuser passage, a dynamic seal between said .drive shaft and said housing comprising a small cen- 5. In a centrifugal pump, the combination of a drive shaft; an impeller rigidly secured on one end of said drive shaft; said impeller comprising a hub, a set of impeller blades mounted on said hub having the leading side rounded to a thin tip, and a rigid stiffening member secured to the one edge of each said blade; an impeller housing surrounding said impeller having an aperture through one side thereof for rotatable mounting of said drive shaft; a fluid inlet passage to said impeller blades through a side opposite said one side of said impeller housing; a circular recess in said one side of said impeller, said stifiening member rotating in said circular recess; an annulus haivng a semi-circular cross section in said irnneller'housing surrounding said impeller blades, a removable member having a double cone diffuser passage therein mounted in an aperture in said housing, said diffuser passage being composed of a first cone portion having an optimum diliuser cone angle and a second cone portion having a steeper diffuser cone angle; and a logarithmic spiral section in said annulus to connect said annulus to said first cone portion of said diffuser passage.

6. In a centrifugal pump, the combination of an irn peller comprising a hub having a center line; and a set of radially extending impeller blades mounted on said hub and having tips defining a substantially cylindrical surface on the rotation thereof concentric with the aforesaid center line, an impeller housing surrounding said impeller, said housing having an annulus of semi-circular cross section surrounding said impeller with the open diametral side of said annulus forming a substantially cylindrical plane parallel with said center line facing said blades, the cylindrical surface defined by said blade tips and the cylindrical surface defined by the open diametral side of said annulus lying in a common plane, said semi? circular cross section of said annulus having a constant cross section over an arc of approximately 270 degrees.

References Cited in the file of this patent UNITED STATES PATENTS 666,234 McRae Jan. 15,1901 730,589 Weiss June 9, 1903 1,467,168 Kaplan Sept. 4, 1923 1,999,163 Allen Apr. 23, 1935 2,044,697 Huss June 16, 1936 2,136,799 MacLean Nov. 15, 1938 2,144,417 Schneible Ian. 17, 1939 2,166,436 Harlow July 18, 1939 2,468,642 Schallenberg Apr. 26, 1949 2,581,504 Wilfiey et al Jan. 8, 1952 2,595,737 Von Rotz May 6, 1952 2,659,375 Grow Nov. 17, 1953 2,835,320 McClure May 720, 1958 2,859,933 Whitaker Nov. 11, 1958 2,873,986 Murray Feb. 17, 1959 2,916,198 Weisel 'Dec. 8, 1959 2,936,774 Holleyet al May 17, 1960 2,973,894 Kimball et al Mar. 7, 1961 3,071,313 Weisel Jan. 1, 1963 FOREIGN PATENTS 212,879 Great Britain Jan. 30, 1934 566,336 Great Britain Dec. 24, 1944 651,627 Great Britain Apr. 4, 1951 342,021 France June 27, 1904 900,706 France Oct. 16, 1944 1,059,223 France Nov. 10, 1953 378,091 Germany July 10, 1923 652,168 Germany Oct. 26, 1937 499,890 Belgium Mar. 31, 1951 97,910 Sweden Jan. 30, 1940 OTHER REFERENCES Publication: Centrifugal Pumps and Blowers, by Austin H. Church, copyright, 1944, pages 19, '20; 118-128. 

1. IN A CENTRIFUGAL PUMP, THE COMBINATION OF AN IMPELLER COMPRISING A HUB AND A SET OF IMPELLER BLADES MOUNTED ON SAID HUB, AND IMPELLER HOUSING SURROUNDING SAID IMPELLER, AN ANNULUS HAVING A SEMI-CIRCULAR CROSS SECTION IN SAID IMPELLER HOUSING SURROUNDING SAID IMPELLER BLADES, A CONE DIFFUSER PASSAGE IN SAID HOUSING, AND A LOGARITHMIC SPIRAL SECTION IN SAID ANNULUS AND EXTENDING 